1. Field of the Invention
The present invention relates to a safety guard installed on a roadway at which a vehicular impact is expected, and more particularly to a vehicular impact absorbing apparatus having cushion pins, which ensure effective arrest of vehicle impacts.
2. Description of the Prior Art
There are several general types of roadway safety facilities, including for example, guard rails for protecting vehicles from deviating from the road and median dividers for preventing intrusion of a vehicle into the opposite lane. Further, safety guards or crash cushions are installed alongside roadways in front of obstructions such as concrete walls, the ends of dividers, toll booths and the like for protecting them against vehicular impact as well as protecting passengers during a car crash.
The guard rail and the median divider seldom collide head-on with a vehicle as they are disposed along by the road. However, the safe guard is apt to collide head-on with vehicles since it is located infront of the driving direction of oncoming automobiles.
In the event of a head-on collision with the safe guard, enormous impact energy is applied to the vehicle which can result in a fatal blow to the vehicle and passenger. Therefore, it is desirable that the safe guard effectively absorbs kinetic energy of an impacting vehicle to minimize injury of passengers and to reduce damage to roadway facilities as well as the vehicle.
A common type of safety guard is formed by a concrete structure or a cushion using worn tires or polyurethane foam. The safety guard on a concrete structure may protect roadway facilities using a simple construction at low cost, however it does not function to absorb vehicular impacts at all. As a result, it presents a serious roadway hazard to vehicles. In the case of the cushion safety guard, it is good at absorbing impact energy, however it returns the impact energy as repulsive power which sends the impacting vehicle back into traffic at a steep angle. This may cause secondary collisions on the roadway with other vehicles.
To overcome these problems of the conventional safety guard, various vehicular impact absorbing apparatuseshave been proposed, for example, in Korean Patent No. 0348707, U.S. Pat. No. 5,868,521, and PCT International Publication No. WO 00/52267.
Korean Patent No. 0348707 discloses a vehicular impact absorbing apparatus having an array of rubber barrels filled with a cushioning material. The rubber barrels are supported by a steel plates buried in each barrel and slidably mounted on a single centered rail. The barrels following the front barrel are provided at an inner side thereof with a wave-shaped steel plate. The rear end of barrel array is fixed to a roadway obstruction by anchor bolts. In a crash, the barrels are retracted along the rail and compressively transformed to absorb the kinetic energy of an impacting vehicle. The wave-shaped steel plate restrains the repulsive force resulting from the impact energy.
However, since the cushioning simply depends on the physical transformation of the cushioning material, the cushioning effect may be affected by the characteristics of the cushioning material, and it is difficult to fully cushion several tons of kinetic energy.
Although this may be overcome by extending the length of the barrel array, it may be limited by conditions of the roadway. Further, since the barrel array is fixed to the concrete wall, it can not be installed at the location where concrete walls do not exist, such as the ends of median dividers and the front of simple branched roads.
U.S. Pat. No. 5,868,521 discloses a highway crash cushion including an array of diaphragms each of which has a guide slidably mounted on a single central guide rail, a plurality of energy absorbing elements disposed between the diaphragms, and an array of fender panels extending alongside the diaphragms. In axial collapse, the diaphragms move closer to one another, the fender panels telescope over one another, and the energy absorbing elements are compressed. Since this crash cushion also absorbs the kinetic energy of an impacting vehicle as the crash cushion collapses axially, it may require a considerable axial length of the crash cushion in order to absorb several hundred tons of kinetic energy. Also, it is costly to repair and rebuild the energy absorbing elements following a collision.
PCT Publication WO 00/52267 discloses a crash cushion formed by a pipe rack frame that retains a number of axially disposed cushion barrels. The pipe frame is provided with a slider which constrains the barrels. The barrels are crushed to absorb a vehicular impact. Using such a crash cushion, it is also difficult to fully absorb several tons of impact energy.